As part of the Environmental Protection Agency's (EPA's) continuing effort to develop the basis for listing certain refinery wastes as hazardous, fuel oil tank bottoms were characterized for semivolatile organic compounds including selected polycyclic aromatic hydrocarbons (PAHs).
No. 6 fuel oil samples were collected from four areas, one in Kansas City and three in Northern California. Soxhlet extraction with methylene chloride, followed by fractionation on alumina, were used to isolate the PAHs in fuel oil samples. The sample extracts were analyzed by high resolution gas chromatography and gas chromatography/mass spectrometry. Total selected PAH concentrations in the fuel oil samples ranged from 71 to 6,560 ug/g. Higher concentrations of other aromatic compounds including alkylated PAHs and sulfur-containing aromatic hydrocarbons were also detected in the samples.
Additionally, laboratory-scale soils columns (2 cm ID and approximately 10 cm long) were used to model the transport of oily waste in the subsurface and potential migration into the groundwater. In one set of the experiments, the oil was introduced on the top of the soil using a disposable minipipet and was then allowed to migrate freely. In the second set of experiments, the soil columns were subjected to a small pressure using pure nitrogen gas. All the studies were conducted at room temperature and the soil columns were saturated with water prior to the addition of the fuel oil.
Several oil mobility studies were performed with fine and coarse soil. The fine soils initially showed no visible mobility for the fuel oil sample during the 17-day experimental period. However, additional experiments using oil/soil ratios of 1:1 and 1:2 (30 g of soil) showed movement of the fuel oil through the entire length of the fine soil column (10 cm). The oil moved through the coarse sandy soil column and also eluted from the coarse column when the same oil/soil ratios as above were used. The fuel oil passed through the columns with little absorption (in a matter of minutes or hours) when the columns were pressurized at approximately 20 psi with nitrogen gas.
In a related study, several Toxicity Characteristic Leaching Procedure, “TCLP” experiments were conducted to assess the feasibility of using TCLP for this type of oily waste and to compare the TCLP results with the corresponding soil column studies. In light of the results obtained in this set of experiments, the applicability of TCLP to this type of oily waste must be cautioned. Furthermore, due to dissimilar processes and experimental conditions involved in the TCLP and column studies, it was concluded that comparison of the two procedures may not be appropriate.